Supersonic harass me 3 years after I closed my account

I closed my account with Supersonic 3 years ago due to their very poor service. Yesterday out of the blue I received a threatening sms saying if I don't pay my account they will hand me over. When I phoned them they say they can't access my account to check. Did you perhaps thought it's because the account has been closed for 3 years. Supersonic is not doing very well and are in the process of liquidation and now like Multichoice and SABC they try to harass old paying customers to try and ***** more money. If I don't get an official apology from Supersonic by end of business I will take legal action.